Using Flow to Parse Case Subject Line to populate a custom lookup field

I want to create a flow that will parse out the case subject line to populate a custom lookup field on a case. Our subject line contains a Quote number that starts with a SQ or SMQ followed by 6 numbers. I want to pull in the quote number to the custom lookup field from the subject line. I am new to flow so any help is appreciated. 

Examples of subject line: 

1. SQ459927 - A3im FW: A3im New Purchase Order
2. FW: [External] PO P35072 for SQ459920
3. Process SMQ666666

#Salesforce Flow #Email-to-case #FlowBuilder #Salesforce Developer