This is a guide on how to transfer saves from an original n64 cart to NSO. While this isn't an exhaustive list, this should help get you started. Each save is different and has different instructions on how to transfer it depending on what kind of save it is. Please use the game list table to see how each game should be transferred.
NOTE: You will need a jailbroken switch in order to perform this. I personally use JKSV to transfer my saves back and forth.
Copy and paste the .eep
file to the save directory and rename it to cartridge.sram
.