Written in JSON and JavaScript, consisting of Resource Packs (visuals) and Behavior Packs (logic/mechanics).
Before attempting a conversion, you must understand why these formats are not interchangeable. Convert Jar To Mcaddon
Before you can convert anything, you must identify what the .jar file actually is. Written in JSON and JavaScript, consisting of Resource
If your .jar file is purely a (a visual change that adds no new items), you are in luck. Converting a Java texture pack to Bedrock is highly automated. Written in JSON and JavaScript
Converting a Java mod to a Bedrock is essentially a "porting" process. Because Java and Bedrock use different coding languages (Java vs. C++), there isn't a one-click button to do this perfectly. Instead, you have to extract the assets and rebuild the logic.