If it must be done inside of Excel, one approach is to format the data using SPLIT and CONCAT. If necessary, the CONCAT might even be rearranged.
Another approach, and the one I use 99/100, is to import the data into Power Query, perform any necessary transformations, and then export the cleaned-up and ready-to-use data to another page (or even another workbook).
Assuming that you actually have a header "Date" in A1, and the data in question was in A2:
- Ctrl+T to turn it into a Table
- From the Data tab, "Get Data from Table/Range"
- From within Power Query, right-click the Date column, select "Replace values".
- Value to Find "."
- Replace with (leave blank)
- Results: 19032023
Power Query 1