At this time templates and community solutions for Google Sheets are not compatible with Excel so you would want to migrate your existing transaction data into Excel.
How to migrate bank data in Google Sheets to Excel:
Open your Tiller-powered Google Sheet.
Open the File menu at the top of the Google Sheet.
Choose Download As…
Choose your file format, either CSV or Excel.
Copy/paste your Transaction data into the Excel workbook you want to connect to Tiller being sure that you pay attention to the column order in the Transactions sheet. The columns are slightly different in Excel vs Google Sheets for our Transactions sheets.