Maybe for starters look for your trainer ID? Take your trainer ID, convert it to hexadecimal, then swap the placements of the digits around for endianness.
For example, trainer number 10303 is 0x283F in hex. So in a save, it’ll be stored as 3F28 (First two and last two digits are swapped). if there’s any leading zeros, make sure to include it for the swap. Now, open the ROM in a hex editor, and Search, find hex, insert your digits, and search all. Make take a bit.
I can’t give exact steps cause every hex editor is different, and I’m not by my com so I can’t recommend the one I use and show screenshots. In any case, let us know how many results it shows you.
If that fails, or has too many results, I suppose the next thing we can try is to find your in game name. What’s the exact IGN you’re using for that game?