Finding last cell in a column

Hi friends I am going to write a Function in VBA that I should have first cell and last cell in a column. the first is easy but I don't know how I can do it for the last cell.
I don't know what should I write instead of x in the lastCell.
I hope you can help me

firstCell = Cells(1, 1)
lastCell = Cells(x, 1)

Something like:

Code:

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Sub test()   
    Dim FirstCell As Range
    Dim LastCell As Range
   
    Set FirstCell = Cells(1, 1)
    Set LastCell = Cells(Rows.Count, 1).End(xlUp)
   
    Range(FirstCell, LastCell).Select
End Sub

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Code:

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Sub M_snb()
  sn = sheet1.cells(1).currentregion
  msgbox sheet1.cells(ubound(sn),1)
End Sub

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