Game save question

Well I want to transfer my heart gold game save to another Heart Gold ROM, and I don't know how to do that D: Can someone tell me how? I'm using No$GBA if that helps.

Just make sure that save file(.nds) has the same name with the rom(.nds).
e.g Pokemon.sav = Pokemon.nds

But how do I save the save file?

Your emulator or flashcart will automatically try to use the save file it finds, rather than creating a new one. As long as it is named correctly.

If your save file is from No$gba previously, just rename it.
You can find it from your BATTERY folder in your no$gba folder.

When I tried to rename it, it gave me a warning message that it might become unusable if I change it. Should I click Yes or No? (Yeah I know, I'm careful)

Put .sav at the end of file name.

The rom is .nds file, so do I change the save file to .nds or do I change the rom to .sav?

No, the save file should be .sav, and the rom should be .nds

When I used my No$Zoomer I opened the new rom I downloaded, but the save file was not there. Was there anything else I was supposed to do?

Have you put the save file(.sav) into the BATTERY folder?