Do you want to migrate your content for free form On premise to SharePoint Online in Office 365, Microsoft has a tool called SharePoint Migration that we have discussed previously in this post
Microsoft announced The availability to Migrate from SharePoint 2010 from this tool as previously it was supporting 2013 only now if you have 2010 SharePoint On premise you can do migration as SharePoint 2010 will soon reaches end of extended support (October 13th, 2020)
To start using tool go to this link
For more resources:
Assess your SharePoint Before Migration
Checklist for Migration between SharePoint versions
Extra posts:
Free SharePoint Migration tool to SharePoint Online and Office 365 
Microsoft 365 Migration Tool A Complete Guide 
Asses your SharePoint before migration to Office 365 
SharePoint Online Page Diagnostics Tool 
SharePoint On Premise Diagnostic (OPD) Tool available 
June 2019 CU for SharePoint Server is available for download