Answered
The Import went fine.But Invoice No,Check No are missing in QB
I have followed your field mappings and imported my Invoices,Check
Expenses & Purchase Transactions sucessfully. But I could not able
to see the Invoice No,Check No & Purchase No in QuickBooks Online?
In Excel Transactions, Import Settings section is available in Step 4 of Import.(Please refer the attachment)
In the Basic Settings,Please enable "Assign Transaction Reference Numbers(Invoice No,Bill No,Check No & etc) from file" option and save the settings.
This should persist invoice / check / expense / purchase numbers in QuickBooks Online.