you will need to be able to read instructions.
you will need the PC version of GTA III. (other versions might work).
You need to use txdcnv to convert the game files to native formats.
Create a directory for the output files.
I have only built txdcnv for Linux x86-64, sorry about that, you will have to use re3-txd.3dsx or compile from source.
./txdcnv [gta3 root] [output root].
The [output root] will now look like:
fonts.txd generic.txd gta3.img menu.txd particle.txd
frontend.txd gta3.DIR hud.txd MISC.TXD
LOADSC0.TXD LOADSC15.TXD LOADSC20.TXD LOADSC2.TXD LOADSC8.TXD SPLASH2.TXD
LOADSC10.TXD LOADSC16.TXD LOADSC21.TXD LOADSC3.TXD LOADSC9.TXD SPLASH3.TXD
LOADSC11.TXD LOADSC17.TXD LOADSC22.TXD LOADSC4.TXD mainsc1.txd
LOADSC12.TXD LOADSC18.TXD LOADSC23.TXD LOADSC5.TXD mainsc2.txd
LOADSC13.TXD LOADSC19.TXD LOADSC24.TXD LOADSC6.TXD NEWS.TXD
LOADSC14.TXD LOADSC1.TXD LOADSC25.TXD LOADSC7.TXD SPLASH1.TXD
Mipmaps are actually 100% necessary.
They drastically improve performance and memory management.
Older versions did this on the 3ds but it took too long.