Just as the title asks, how do I set the startpoint for an autonumber after field creation? The field is an external Id and to avoid conflict with the external system, I need to move the id up a few numbers.
You can convert the field type to text, then convert it back to auto number. When you convert it back, you'll have the option to set the starting number again. I might do this after hours if there is a danger of a record being created while you're doing the field conversion.
Changing the field type is a good idea. Alternately, if you're only going to move the auto-number up by a few numbers or even a few tens of numbers, you could insert some records and delete them. Crude but effective.