89 pa

my 89 pa will not shift out of first gear was told it was the vacum modulator is that true

That is possible, pull the vacuum hose off of the modulator and see if you can detect any trans fluid in the hose or fitting. If so, it is the problem! You could also have other problems, like shift a valve stuck in valve body. Leave it in drive, and open the throttle wide open through first gear until it jumps into second. Sometimes, this will clear an obstruction in the valve body.