If a plant produces 5.81 mol of c6h1206, how many moles of co2 are needed? Please help!?

I guess you mean C6H12O6.
The reaction is
6H2O + 6CO2 --> C6H12O6 + 6O2.
It takes 6 moles of CO2 to make 1 mole of glucose, so it takes 34.86 moles of CO2 to make 5.81 moles of glucose.

Let mass be 1 g.
Molar mass (M) of C6H1206 = 12.0 x 6 +1.0 x 12 + 16.0 x 6
= 180 g/mol
Molar mass M(C02) = (12.0+16.0 x 2) x 1 g/mol = 44 g/mol
No. of moles per g in CO2 = mass/molar mass = 1/44 mol