regex to extract a portion of a string -

i looking regular expression search portion of string , extract subsequent parameter...

source strings here:

 5288470f7e7155f1a19d7236f837d3cc:120// 5288470f7e7155f1a19d7236f837d3dd:20// 5288470f7e7155f1a19d72daff:9302// 

the source string length , follow same pattern: id:result//

i need able search string longer id , extract subsequent number between : , // pattern. give search string "5288470f7e7155f1a19d7236f837d3dd" - need result "20"

can help?

thanks

using grep can in following way:

grep -po "(?<=$target_string:)\d+(?=\/\/)" 

this print number require. regex used perl compatible.