In automation for Google Sheets - how to add an automatic number to each new column?

Hi
I have an automation that transfers the details of the record to a new column in Google Sheets.
I want the first column to write the number according to the report adders. That is, someone else joins Google Sheets - it writes the number 2 next to it. After someone else joins, it writes the number 3 next to it.

Thank you!