In Latin, I understand the suffix "que" means "and." My question is what does the suffix "que" mean when there is only one word?

It would normally still mean 'and' in that use. As Bedlam asked, give the context. Translating single words in Latin is often meaningless.

BTW, 'We conquer Power and Mountains' is absolutely a good translation for Vires Montesque Vincimus.

That is the whole sentence. VIRES MONTESQUE VINCIMUS Is the motto of the 87th Infantry Regiment.

There seems to be several translations floating around.

"We conquer men and mountains" " We conquer the strength of mountains" "We conquer power and mountains" are all translations I've seen. There are probably more.

I will present the whole phrase as requested:

It is the Latin motto of the 87th Infantry Regiment of the U.S. Army. The whole motto is "Vires Montesque Vincimus". Vires is first person plural for power/strength; Vincimus is first person plural for conquer/overcome. The so-called "official" Army translation is "We conquer Power and Mountains". There is absolutely no way that translation is correct as even the Army kept attempting to refine the translation. If someone with scholarly knowledge could help it would be highly appreciated if you would also allow me to present you as a source to the U.S. Military Institute of Heraldry. Thanks all.

Can you give us the context, like the whole sentence?