I need to migrate several site collections from SP2010 to SP2013. After I migrated the sites to SP2013 farm and create a evaluation copy, the site customized layout are all lost. (It is expected since Microsoft said I need to re-create the masterpage and theme). However one of customized webparts also disappears. It is a natvigation menu webpart. This webpart will show buttons according to a list "menu items" under the site collection. The list have be migrated successfully but the webpart is not showing anywhere.
I have setup the migrated the same site collection in SP2010 mode. The menu webpart do exist. I can check its "webpartid" by view source in the browser.
May I know how can I import the webpart into the SP2013 enviroment again? Thanks for advice.