Need to add fax number to copier our copier number 3350 did'nt get a manual

On these machines there should be a button for set up or maintance on the fax machine.
If you can find this you may need to scroll and find the setup menu and enter in the fax setup area to add these changes. There are other sections to add date and time and store copies to memory or even print and set junk mail to off.
If the machine is old you may try the internet to search for a manual for this product or seek the vendor for publication manuals.
Good luck