Afaik, those codes are merly action replay.
Anyway, to find for harvest moon, do this:
Download pj64 (homepage is in my sig), open the Project64.cht in the directory where you installed it. Search for "harvest moon" when opening it in notepad. Make sure that it is the version you're using (ie (U) or (E), it's usually noted at the game name).
Look for the cheats you want. When you find it, go a little right, after the comment, you'll find the cheat address like 80XXXXXX XXXX. Copy all that and paste into the nemu cheat-file. Remove the "80" in the beginning and make it as a cheat for nemu.
That simple.