FX0 Module Count?

If I get a blank TDM400P card:

I have an internal VoIP network. I want to use NORMAL PSTN connection for all outside lines. I have 4 PSTN lines.

How many FX0 Modules will I need? 1? or 4?

refined: Will I need a module for each line? Or 1 module for all 4 if they will all have Same Exact Config???

4 FXO modules would do it…