I am not sure why you would be trying to install phpBB 3.0 as support for it has less ends at the end of this month.
I would suggest that you download the latest version (phpBB 3.1.10), remove all the files that you have uploaded and start again.
David Remember: You only know what you know and - you don't know what you don't know! My CDB Contributions | How to install an extension I will not be accepting translations for any of my extensions in Github - please post any translations in the appropriate topic. No support requests via PM or email as they will be ignored