Step one: save your data before using new functions, so you don't lose
anything!

One way to do this is to insert some columns, then highlight your
"legal" numbers column. On the menu at the top click Data Text To
Columns and in the prompts that follow indicate the period as your
delimiter. This function will separate each entry into its component
numbers, so from there you can highlight the rows and perform a
multi-column sort ("Sort by Column A, then by Column B, then by Column
C").

Greetings from Virginia, USA, near Washington DC.