If you don't have ChemDraw installed, several web-based tools can handle the conversion:

If you have access to ChemDraw (Windows or macOS), this is the gold standard.

Are you looking to convert of files?

Step-by-step: using intermediate tools (if no ChemDraw)

Then use:

Increase the DPI setting during export. Never take a screenshot of a small CDX file and enlarge it. Always export directly at high resolution.