OK boys and girls, let's review our basic chemistry regarding noble gasses.
1) They don't form compounds with anything!
So He3 and He-3 are unambiguous because they CAN'T refer to a tri-helium molecule!
Now that being said:
1) There's quite a bit of He-3 on the moon and you can get it out of the regolith by just heating it up and capturing the resulting gas.
2) There's WAY more He-3 on Uranus and Neptune, and if we had a nuclear thermal rocket motor we could go get it!
3) Yep, He-3 fusion is way out in the future, but if we had tons of He-3 available, it'd be here way sooner!
4) He-3 is SO expensive, you can almost assuredly make a business case now for mining the moon for it!