Power inverter

My CPAP is multi-voltage. Are you sure your CPAP is single voltage?

Do you need an inverter to change AC/DC, or a converter to change from 110-120v to 220v?

Have you looked closely at your device to see what voltage it takes? It may already be dual voltage and need only a plug adapter

I am betting your C-PAP is dual voltage.

Thanks for info. I’ll be checking it to see it’s multi voltage. I know it will need a adapter for cord.

If you're going to Germany, just the typical Europe voltage adaptor will be fine for it. Rick Steves sells them for a very reasonable price and I would suggest getting a few to take with you, as you will probably need them for other things. https://store.ricksteves.com/shop/p/european-power-adapter

And as others have pointed out, you will almost undoubtedly find out that you do not need a converter for your CPAP.

voltage adaptor

?

You probably mean a "plug" adapter.

If you have a portable model, and it's like every portable I've seen, it has a separate power supply/charger that uses a two bladed (type A) American plug. If so, all you need is the adapter to which Mardee linked, called a Europlug (Type C) adapter.

If your cpap has a grounding (type C) American plug, with the round pin third prong, the Europlug adapter will not be suitable. In Germany, use this adapter instead. Note: that adapter says it works everywhere on the continent except Italy and Switzerland, but receptacles in France, Belgium, Poland, and Czechia have a ground pin protruding in the recess and the plug requires a hole in the surface with the two pins. I don't see that hole on the pictures of that adapter (it might be hidden behind one of the pins), so I can't say for sure it would work in those countries, but it is fine for Germany.

As the others have said, you will probably only require an inexpensive Plug Adapter, which will adapt the North American style plug to European style outlets.

My CPAP is designed for use on a voltage range from 100-240 VAC, 50/60 Hz, and uses a two pin plug (no ground). If you check the power supply unit that came with the CPAP, look for the words "Input Voltage". That will indicate whether it will work on European electrical systems (it's very likely that it will).