If I wanted to make 250ml of a NaCl of a solution at a concentration of 3g/ml, how would I dilute the 1.0M solution?

I hope this isn't a homework question!
3 g/ml is 51.3 M. I don't believe this is possible.

did you mean 3 g /L?
that is = 0.051 M (FW of NaCl = 58.44)