CFM converted to PSI

CFM converted to PSI   (05/18/2017, 2:42 PM)

hello I have a 140 cfm usage air gun that uses 3.4 US gpm of water creating 13.5 lbs per foot of thrust.

I would like to understand what this would be if converted to PSI so that I can work out the cleaning power

Can someone help because the manufacture of this gun are not helping?

Thank you