Generally speaking you can simply upgrade and the version 11 installer will simply convert your configuration. I would strongly encourage you to upgrade to 10.2.4 before upgrading to version 11. For minimal pain I would normally suggest you go from 10.2.4. to 11.3.0, and from 11.3.0 to whatever version you would like to land on.
Note that the version 11 parser is stricter than version 10, and it may still fail to load. At that point look in /var/log/ltm for the reason why. If it is not obvious, run:
/usr/libexec/bigpipe daol
This will attempt to load your v10 configuration again. Look in /var/log/ltm again. You may need to tweak your version 10 configuration (look in /config/bigpipe). Iterate over the last set of instructions until your configuration loads then run:
tmsh save sys config
Which will save your configuration to disk. At that point you should be done. If things get really hairy open a case with support.
Important note: Make sure that you reactivate your license before you upgrade.