Documentation on how to use data prepper

I am currently using logstash 7.10. Is there any documentation on how to use data prepper. I have several logstash config files that have multiple conditionals for destination index name patterns.

You can try the official OpenSearch docs, there’s a section for Data Prepper.
There’s also more elaborate material on the respective repo. For example logstash_migration_guide may be of interest to you.