there a few options and depends on some situations. IF all you need is to VISUALLY see the added 1 then you can do that using a Custom Number Format. IF you need actual values then you can add a column with a formula like ="1-" & A1:A100 and at the end you say "and format the list"? again custom formatting options for visual or in the above you can add formatting using TEXT(.... , "formatting style")
there a few options and depends on some situations. IF all you need is to VISUALLY see the added 1 then you can do that using a Custom Number Format. IF you need actual values then you can add a column with a formula like ="1-" & A1:A100 and at the end you say "and format the list"? again custom formatting options for visual or in the above you can add formatting using TEXT(.... , "formatting style")