REGEX - Matching pattern to extract value between two strings

I need to extract a value between two strings --> "ifName." and " = STRING: VDSL 0/n/m" where n and m are variable and are going to be set by me at runtime.

The point is that i need the last number, for example, if i have n=3 and m=9 i will match this "4160774720". I hope i explained well.

ifName.4160774464 = STRING: VDSL 0/3/5 ifName.4160774528 = STRING: VDSL 0/3/6 ifName.4160774592 = STRING: VDSL 0/3/7 ifName.4160774656 = STRING: VDSL 0/3/8 ifName.4160774720 = STRING: VDSL 0/3/9 ifName.4160774784 = STRING: VDSL 0/3/10 ifName.4160774848 = STRING: VDSL 0/3/11 ifName.4160774912 = STRING: VDSL 0/3/12 ifName.4160774976 = STRING: VDSL 0/3/13 ifName.4160775040 = STRING: VDSL 0/3/14 ifName.4160775104 = STRING: VDSL 0/3/15 ifName.4160775168 = STRING: VDSL 0/3/16 ifName.4160775232 = STRING: VDSL 0/3/17 ifName.4160775296 = STRING: VDSL 0/3/18 ifName.4160775360 = STRING: VDSL 0/3/19

Thanks to everybody;D Someone save me and my working day

Angelo