Column1 Result
Gi1/0/1 Gi1/0/01
GI1/0/11 GI1/0/11
abcdef5/8/5 abcdef5/8/05
abcdef5/8/56 abcdef5/8/56
ZXCV/bb/rtu/999/75 ZXCV/bb/rtu/999/75
abc/879/134/444444 abc/879/134/444444
ab/11/22/rem/3 ab/11/22/rem/03
ab/11/22/rem/44 ab/11/22/rem/44

Code:
let Source = Excel.CurrentWorkbook(){[Name="Table1"]}[Content]
in Table.SelectColumns(Table.AddColumn(Source, "Result", each Text.Format("#{0}/#{1}",{Text.BeforeDelimiter([Column1], "/", {0, RelativePosition.FromEnd}),Text.PadStart(Text.AfterDelimiter([Column1], "/", {0, RelativePosition.FromEnd}),2,"0")})),{"Result"})