Find A Set Of Numbes In Long String Using RegEx?

Ive been searching the Stackoverflow but couldnt find the exact thread that my problem is this, i want to be able to find and take out any occurances of 8 digits wihtin a string.

Dim SetOfMatches As MatchCollection
Dim MyRegex As New Regex("A^d{8}$A")
Dim TestString As String = "testing 12345678 testing"
myMatches = myRegex.Matches(TestString)
For each Row as Match in myMatches
console.writeline(row.value)
Next

this doesnt not generate any hits. but i want to find the 8 digit occurance in the middle of the string.

I am very basic in RegEx.