I see that you are trying this forum as an alternative Physics Forum for your inquiry. The direct answer to your question is not easy because there are several gas properties used to calculate the required pressure; however, I have an excel spreadsheet program for that calculation using USA units, based upon the reference document noted on that sheet. If you will send me an email at ( albertshous at aol.com ) I am willing to return email you a copy of that program as an attachment. That copy already has an example calculation that I have run for your specific problem. Solving the problem requires adjusting the inlet pressure until you obtain the flow volume required.
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