I use the manufacturers PAR/PPFD charts. If I don't trust the manufacturer, I would find someone doing a PAR test on YouTube or something. I did that for my Mars Hydro TSW 2000 and MH was honest about their readings.
That said, I looked up your TS 3000. Looks like you have 4 plants, their centers probably about 1 ft from the center of the tent. If this is true, you should be at 24-26" from your plants. If they keep the same distance during flower, you'll want to be 18-20" away from the canopy.
For veg you want 400-600 ppfd and for flower you want 600-900 ppfd. The higher ends of these ranges are better, but giving them too much will hurt them. Good luck, feel free to message me if you need some more info.