The StringPosition command returns a list of the starting and ending character positions at which a specified string appears as a substring.

$\mathrm{with}\left(\mathrm{MmaTranslator}\left[\mathrm{Mma}\right]\right)\:$

$\mathrm{StringPosition}\left(''abccbaaccbbaa''\,''cc''\right)$

$\left[\left[3\,4\right]\,\left[8\,9\right]\right]$

$\mathrm{with}\left(\mathrm{MmaTranslator}\right)\:$

$\mathrm{FromMma}\left(\mathrm{`StringPosition["abccbaaccbbaa",\; "cc"]`}\,\mathrm{evaluate}\right)$

$\left[\left[3\,4\right]\,\left[8\,9\right]\right]$