That looks like #1 aluminum thw wire in your 3 phase panel 100 amp panel. Using the middle, use the 75°C column in all gauging all wire sizes. Breakers are typically rated for 75°C max fyi. So your feeders right now are rated for 100amps. (ninth down/six over)
Ok so for 200 amps I recommend 3/0 copper. Or you can use 250 mcm al. wire. The copper wire will require a 2" conduit and the al. wire will require 2 1/2" conduit. Al. Suck and 2 1/2" parts typically can't be purchased at your local hardware store either. Also by the looks of the lugs the panel might only be rated for 100 amps maybe 125amps.
3 phase panel gives you ample room for proper electrical distribution at 100 amps. Ive ran +11k watts in lights, ac, fans, pumps etc on less than 100amps on a single phase panel. Hope that helps.