For the Power Bi interview, obviously, the main thing is you should have a good knowledge of Power Bi and the ability to create impressively and useful visualizations in Power Bi.
If you go for an interview, all the candidates know Power Bi and there will be multiple candidates appearing for the interviews. The main thing is you need to focus mainly on the basics of Power Bi. If you are good at basics it is not that tough to crack any interview.
If you don’t know something, good to accept that you don't know but it is your responsibility to ensure the interviewer that u you are willing to learn new things and keep yourself updated in the Power Bi field.
You can check out this blog on Power Bi Interview Questions for more frequently asked questions in an interview with simple and lucid explanations.
Also, you can watch this video for more information: