OBD2 plug in no power, on 1998 mer/Benz slk230

no year told (omg even 1996 to 2020 and are NOT THE SAME)
nor the words Mercedes-Benz SLK230
no country told, and car are not the same all over the world
sad no.
fuses blown or CB circuit breakers tripped

your windows move first , check fuses and clean your window may be sticking due to dirt.

There is a couple of places it could be under the bonnet is one the other is on the door piller

Go to online store reliable they have repair manuals I am sure you will get the solution. Here's the link
MERCEDES BENZ SLK SERVICE REPAIR MANUAL 1998 2004 DOWNLOAD

look for a thick hose at bottom of radiater...

where is the fuel pump relay located in a 1998 mercedes slk230?

It is located under the car in front of the fuel tank in a tray.

another suggestion is that you need to have the code re-entered for the hardtop. I just had mine repaired due to a busted hydrolic hose, and the mechanic had a hard time getting it to work properly and ended up having to re-enter the codes.