I have an extension number to call, but there are no prompts to dial an extension. Any suggestions?

Dial the main number. Ask to be transferred to the ext.
repeat as necessary until it actually happens.

you gotta ask for Sarah first,
and she'll put you through to crabwell corners

Local Cabela's here uses 314-225-0100. Number to warehouse is 314-225-0113. No idea if the system is the same at your location, but that may translate to extension 13 or 113.

I've had a measure of success with just pushing buttons on the keypad randomly.

*8 or ... 00 (two or more 0) often work to get you out of a dead end loop or to an operator / main menu.

I finally just waited on hold for a very long time this morning and finally got a person. I was told there is no way to dial an extension. Needless to say, what I wanted to order was sold out anyway.