Changing excel data source URL from Web to SharePoint online

Hi,

I have one PBIX file containing about 20 datasets sourced from excel file. the excel files are stored in an On-prem SharePoint library and connected to Power BI Desktop through Web URL. All the datasets have a lot of Measures  and Columns for calculations Power BI Dresktop. Now I am moving all my excel files from SharePoint On-prem to SharePoint Online. 

In this case, I need to change the connection string and its different from the earlier. I also want to keep all my calculated Measures and Columns working fine without recreating. Would you please suggest what is the best way do this?

Thanks in advance.