Trying to combine two spreadsheets with one identical column header

Hi, any help will be gratefully accepted - first time posting so please bear with me!
I am trying to combine two spreadsheets which both have the same unique customer reference number in one column.

I need to transfer/ copy about three columns from the one spreadsheet to the other. ie a notes section and activity section from one which are columns in the same row as the unique customer reference number, to new columns in the other spreadsheet on the same row as the unique customer reference number.
I fear this may not be too clear - but to simplify:

Sheet1:
Column headings:
Customer number
Start date of contract
End date
Arrears

Sheet 2:
Column headings:
Customer Number
Date last site visit
Date last contact
Customer Service Rep

I need
Sheet 3:
Customer Number
Date last site visit
Date last contact
Customer Service Rep
Start date of contract
End date
Arrears


Many thanks for your help.
Julia

Brilliant! Thanks so much for your help.
Kind regards,
Julia