Float is the way computers these days tend to account for decimal numbers (if you are bored then
https://www.bbc.co.uk/bitesize/guides/zscvxfr/revision/3 ). Sometimes however, and against what is normally good programming practice, devs use floats for things that don't need it, or sometimes need it for other reasons (like it needs to be used in a further equation that does use floats so makes sense to keep it in that).
Your basic cheat search for a number, or things that act like them (if doing the higher or lower searches thing), will possibly then fail. I imagine you have met a buggy game or two over the years and thus games being programmed in a rather suspect manner is hardly going to be a new idea, if playing hacker you then get to play to what is rather than what should be.
Personally I would say jumping in on the Switch is somewhat jumping in at the deep end. Sure it does function the same in most principles as anything going back to... anything that is technically a programmable computer driven game but there are enough little annoyances, frustrations and quirks both because of security and because of modern coding practices that I am not sure it is the best learning platform. If it is the only thing that will hold your interest for right now then you can get it done but I would pick almost any older handheld, consoles older than the PS3/360, and PC games maybe from slightly before that (the modern coding practices kicked in earlier on the PC).
My usual guide to basic cheat making
https://web.archive.org/web/20080309104350/http://etk.scener.org/?op=tutorial
As above then a single value changing with on screen might be related somewhere along the line, however it might not be what the game uses. Some games do this as an anti cheat measure*, others just do it because programming is easier (recall the earlier part about floats -- far easier to convert a normal unsigned number to something on screen with fancy text like that than a float or a signed number).
*some games will keep an internal record of everything going on and farm that out to various things (you might give a copy of something to someone but the master list is what matters).
Anyway you can try with floats, I tend not to find most money systems in games be that (especially not what looks like a tie in game using a simple money system -- start doing a complex financial system in a game and that changes, though amusingly it might not use floats any more as they are too imprecise). What I would probably go for first is not an exact number, or even a number increasing/decreasing depending upon what you spend, sell or pick up but just something changing. It should capture any floats that way, but will also handle the game doing something like money = max value - current value for its internal state. It is not foolproof (some kind of changing pointer, value held on the stack/registers**, or certain types of check/protections will not necessarily be caught) but definitely worth a try. Equally while I tend not to find cash in games to be protected either there is the odd programmer that is on the verge of losing the will to live; all that school and then finding themselves programming spongebob game however many years it is after its heyday (I saw an amusing video a while back that noted that every notable meme and templates thereof, and thus presumably most people's memory of it, was series 1 to 3) so going to do something fancy rather than have brains dribble out of their ear.
**returning to the copy of a day planner diary or something. Someone nefarious could come in and erase something for you, however if you took a picture of it before you left and operated from that you would be blissfully ignorant of the nefarious person. Same idea here but the data is taken from where it normally sits in memory and the game uses its copy for a while before it has to write it back down rather than constantly going back to memory (which can slower than ideal for some programming methods), and you are the nefarious one sneaking in to change things.