How to upgrade data from elasticsearch 2.4 to 5.6

i need install what plugin at elasticsearch 2.4 and 5.6?

Nothing.

i already add 'reindex.remote.whitelist: oldhost:9200' at elasticsearch 2.4/ but still same.

No. You need to add reindex.remote.whitelist: 10.88.4.253:9200 in the 5.6 node settings.