Normally you just put the save where the savegames are stored (same folder as the roms or a saves folder depending on your setup) having the same name as the rom, just another extension normally .sav .
Some wear old clothes and look old, others think wear vintage clothes and look cool. I think the GBA is in the cool corner and guess where the ds phat is...
A photo of the pcb would help, then you know might found out which card you've got and which flashcard files you need.
Downloading roms is a google problem.
I buy there regularly: compare, check, check the size, check the price and don't buy SD-cards.
I saw people ordering a gun getting the picture of the gun (exactly as in the description if you read all the way down). I bought rp2040's, leds electronics...
I may try the new ram site, and download more RAM to my Switch. Not sure if ddr3 is the right ram
for it tho. Edit- no it uses floppy Ram, just like @AncientBoi