Newer projects like by Stonebyte aim to automate the conversion of .jar mods into Bedrock-ready .mcaddon files by handling pack generation and file structuring.
Since code logic cannot be converted automatically, you must rebuild the behaviors manually. Convert JAR to ZIP Online | No Software Needed how to convert jar to mcaddon portable
Before discussing "how," one must understand why a direct conversion is impossible without significant rewriting. Newer projects like by Stonebyte aim to automate