Can someone guide me to the part number or where I can get a replacement hose like this one. 
Mine is cracked and I need to replace it.

Here. Get acquainted with this site, too.

I’m assuming this is why my k100 has lost power.
Won’t pick up speed like it used too. Is loss of power a symptom due to this?

It could be one of the many reasons for power loss by a fuel mixture that's too lean and replacing it will let you know if it's the only reason. Cracked rubber manifolds attaching the plenum to the throttle bodies, cracked or missing caps on the throttle body vacuum ports, and a failing throttle body-to-fuel pressure regulator hose can also contribute to power loss. Valve clearances out of adjustment and throttle bodies out of balance could be in the mix, too.

Ecarranza wrote:I’m assuming this is why my k100 has lost power.
Won’t pick up speed like it used to. Is loss of power a symptom due to this?

Once you replace the engine breather hose, part number 11 15 1 460 480, and the bike is idling smoothly, remove the oil filler cap and watch the revs change dramatically. This gives an indication how vital it is. Now go look for the items and areas of concern which Laitch mentions if the engine idle is erratic or the bike vibrates more than you feel it should.

I’m waiting on that part to come in and I’ll replace it.
Can it also be my battery that’s not fully charged that can cause a loss of power?
I just plugged it in to charge and the batter was under 50% it’s capacity.