How to Extract SubString between two positions

I have a text column (*emailbody*) in a table (*notification*) which keeps a record of the HTML that went out for a particular email. Somewhere inside that HTML file, there is a line of text that contains the following line: Delayed ${shipmentId} for Carrier Where ${shipmentId} represents the specific Id that was generated for that particular record. Example: **12345** Basically I want to query the column in the table for all the shipmentId values, which unfortunately will involve getting the string positions between Delayed and for Carrier. I understand this will likely involve using one of Postgres' regular expression functions but I'm not quite sure how to do it, or if there's something a little simpler.