Hi @eng_minamaged
here a simple code that I tested.
Sub TextSubstitution()
Dim MyText As Variant
Dim ObjectText As Object
Dim MyPos As Integer
Dim MyLeft As Variant
Dim MyRight As Variant
Dim MyRightValue As Integer
Dim MyNewString As Variant
For Each ObjectText In ThisDrawing.ModelSpace
If TypeOf ObjectText Is AcadText Or TypeOf ObjectText Is AcadMText Then
MyText = ObjectText.TextString
MyPos = InStr(1, MyText, "-", vbTextCompare)
MyLeft = Left(MyText, MyPos - 1)
MyRight = Right(MyText, Len(MyText) - MyPos)
MyRightValue = Val(MyRight)
MyNewString = MyLeft & "-" & Mid(Str(MyRightValue + 1), 2, Len(Str(MyRightValue + 1)))
ObjectText.TextString = MyNewString
End If
Next
End Sub
Code consist of searching on ModelSpace a text and increase by 1 unit the last number after "-".
Code it's working with last digit by one, two or three digits.
Source:

After Running procedure

Before Running procedure 2nd test with three digits

After

I hope this will solve your issue.
Concerning the huge amount of dwg you can enlarge procedure with automatically open file from a list of drawing name with path, apply procedure, save with another name.
I'll show you how soon if you are interested also for this part.
Regards