See https://www.ablebits.com/office-addins-blog/separate-first-last-name-excel/
In situations when you have a column of names of the same pattern, for example only first and last name, or first, middle and last name, the easiest way to split them into separate columns is this:
Select the column of full names that you'd like to separate.
Head to the Data tab > Data Tools group and click Text to Columns.
On the first step of the Convert Text to Columns Wizard, select the Delimited option and click Next.
On the next step, select one or more delimiters and click Next.
In our case, different parts of names are separated with spaces, so we choose this delimiter. The Data preview section shows that all of our names are parsed just fine.
Tip. If you are dealing with names separated with a comma and space like Anderson, Ronnie, then check the Comma and Space boxes under Delimiters, and select the Treat consecutive delimiters as one checkbox (usually selected by default)
On the last step, you select the data format and destination, and click Finish.
The default General format works nice in most cases.
As the Destination, specify the topmost cell in the column where you want to output the results (please keep in mind that this will overwrite any existing data, so be sure to choose an empty column).
Done! The first, middle, and last name are divided into separate columns