i need to find specific string in order to check it,
is there any functionality in visual basic to bring all places with
the same string instead of going one by one?
No.
Consider downloading MZTools.
http://www.mztools.com/v3/download.aspx
Won't do exactly what you are asking but does improves on VB Find
capabilities.
In general, for this type of work you are better off using a 3rd party
programmer's editor that can work with VB's text files. Every
programmer needs to add one to their arsenal sooner or later. Prices
run from 'free' to around $35-50. There are some uber-ones for around
$200 bucks.
If you just want to do a quick peek, check out command utillities such
as Find, FindString, WinDiff, or the 'grep' capabilities of
PowerShell.