Extract number sequence

I have transformed the data of a JSON in a column. Now in each cell is a big amount of numbers and letters. It looks like this:

{“rel”: “self”, “href”: “https://.net/api/report/eExecution/12345678”}]{ “rel”: “self”, “href”: “https://oup.net/api/ret/cution/12345677”}]

I need to filter the number sequences of 8 digits like in this example 12345678 and 12345677 in a new column but sometimes there are also 4 number sequences like this.

How can this be done?