Here are a list of resources you can use to learn how to convert numbers from one base to another.
It is recommended that you watch/read in the order listed:
Overview of other number systems:https://www.youtube.com/watch?v=_97OwCkjh3c
How to convert bases using java: https://www.geeksforgeeks.org/base-conversion-in-java/
Binary to decimal: https://www.youtube.com/watch?v=a2FpnU9Mm3E
Decimal to binary: https://www.youtube.com/watch?v=gGiEu7QTi68
Binary to hex direct: https://www.youtube.com/watch?v=8T4F7WboWPQ
How to convert from any base to any base: https://www.youtube.com/watch?v=hIs3A6gGz2w