If you know where it ends up in RAM then you should be able to find where it first loads that in and work backwards from there.
It is for graphics and I tend to suggest no$gba debug for most people these days rather than vba-sdl-h which that is written for but the workflows are about the samehttps://www.romhacking.net/documents/361/
It might not even be that value, or indeed a value if the health is generated from stats or something. To say nothing of health need not be the same as maximum health which might be a separate concept within the game.
Indeed unless the game has a whole bunch of character classes or something to choose from I would probably not even contemplate a searching approach like that and go right for assembly, and I am normally all about not going right for assembly if there is a reasonable chance or alternative workflow.