Renumbering cells when data inserted and synchronizing across sheets

Hello.
Im definately new to this. Great site! I wish I understood half of what was posted!
My issue, I have a list of departments/shops with prioritys. Now when and item is placed anywhere within the list it must recalculate the following numbers. Ex: If i make a new priorty 4, what was 4 becomes 5, 5 becomes 6 (etc). Each shop also has its own sheet as the list will be hundreds of items. This way they can filter and see the relevant work. These sheets must be in sync with eachother. The attached example has 10.


I really need help autonumbering the prioritys and syncing the sheets.
Anyhelp would be great. Im basically on day 1 here.

Thanks.