Unit of meaasure tm3/h

A bit more context would help here.

What sort of values are they and what for?

what sort of numbers were you expecting?

Is is for a gas or a liquid? At any sort of pressure?

Is it in English?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

tm3/h?
I think all will agree that m3/h is cubic meter per hour. The t is the question mark. The t is often internationally used as abbreviation for ton, and accepted as symbol for this (1t=1000kg) together with standard SI-units. (Same for hour h=3600 SI seconds).

This is probably the nearest you can come to official standards. What tm3/h means in your context has to be explained by the person using the unit if it is not self-explaining.

I absolutely agree with gerhardl.

This site says that "t" stands for metric ton a.k.a tonne, which also agrees with gerhardl's post. I hope you can ask whomever gave you this document to confirm.