Question about MSI B350 Tomahawk

RTFM!
Steht natürlich im Handbuch:

https://www.msi.com/Motherboar...

The power is on, but no signal to
monitor
- Connect the monitor power cord to a
electrical outlet securely.
- Make sure the monitor is turned on.
- Select different inputs on the monitor.
- If 3 long beeps are heard, remove all
memory modules and try to install only
one memory module in the DIMMA2
slot first and then restart the computer.
- If 1 long 2 short beeps are heard,
remove and reinstall the graphics card
and then restart the computer.
- Test with another known working
graphics card.

I wouldn't know that either, it should be in the MoBo manual. For questions like this, https://www.reddit.com/r... is usually very useful because you can get quick and good answers there.