Upgrade 2010 Web Application to 2013 Site Collection

Hello everyone.. I've been searching a few times to upgrade 2010 to 2013. But mostly I've been seeing by using the mount-spcontentdatabase tool. 
The problem is we are trying to use one web application in 2013 for all the old webapps in 2010 and make them site collections with different DBs on 2013. I can't use the import/export-spweb command because it gives me the error below

Import-SPWeb : The version of the package 14.0.0.0 is different from the current version this program supports, 15.0.0.0.

I can't use the mount-spcontentdatabase because it doesn't want the defined path but want's a web application.

Do you have any other suggestions to try ? Third party tool is not an option :(

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AJ MCTS: SP 2010 Configuration MCSA: Windows 7 If you find this post useful kindly please mark it as an answer :) TY