Looks like a trivial stoichiometry, what have you tried and why it didn't work?
So I tried:
Calculating the Volume so I could use M1V1=M2V2
But I don’t know how to calculate the volume. Also converted PH3 to moles (0,0294) but not sure what to do with it next. The moles I converted is with the molair mass of PH3 divided by the one gram. Tried dividing it with 4 since the ratio PO3 with PH3 is 4. So I’m not really sure if I’m close to anything but I really really can’t figure it out..
I tried so many more things but erased them out of frustration sorry.