Queries :: Finding Work Orders That Only Contain Certain Type Of SN

I am new to access but understand how to do a simple query. in this case i have 4 fields in my query. I only want to return work orders where the only SN's for that work order begin with 600 or NEX. when i use the like button it gives me all those work orders, however it doesn't exclude the work orders with other types of SN's. is there a formula i can use that says return work orders that only contain this type of SN?