I do not know how to use the workbench in Moira's shop. I have the 3 ingredients I need for making 10 mm ammo...but it won't let me. Am I supposed to finish a quest first?

You can't craft ammo in F3, only seven weapons from schematics.

( yep, only weapons, like the Enclave said.)

What ammo-crafting mod are you using? You usually have to find or buy a schematic in order to be able to craft ammo.

I bought the schematic for 10 mm rounds. SORRY, I DON'T KNOW HOW TO COPY/PASTE THE LIST...IS THERE A WAY? By the way, this list is not in 100% correct order either. I am using

CRAFT.esm
CALIBR.esm
xcalibr.esm
20th century weapons.esm
AmmopresswithCALIBR.esp
CRAFT wce warmonger addon.esp
CRAFT ammo schematics - CRAFT.esp
xCALIBR ammo schematics_FOS enhancements.esp
xCALIBR munitions.esp
Apocalypse Armory.esp
Apocalypse Armory - CALIBR.esp
Apocalypse Armory - XCALIBR.esp
Apocalypse Armory -DLC enhancements.esp
\

Try the Fallout 3 Mods section.

Those guys should be better suited to clear things up for you.

You can make ammo in The Pitt DLC. Once you complete it you get access to the Amunnition Press.