Select one of the cells.
Look at the formulabar.
If you see the spaces, then select that column and use:
Edit|replace
what: (space character)
with: (leave blank)
replace all
And give that column the number format you like.
If you don't see the spaces, then try reformatting the range.
Select the column
Format|Cells|number tab|Custom
type:
0000000000