unless you have a specific reason to put this data into iNaturalist, i don’t see why you would do so. if you’re just trying to map trees, you have more options and more flexibility doing it in your own setup.
the hardest part is collecting and structuring the data. once that’s done, you can visualize it easily any number of ways. just for example: https://forum.inaturalist.org/t/mapping-of-excel-data/30531/12