  Quite often the zero mode dynamics on solitonic vortices are described by a
non-conformal effective world-sheet sigma model (WSSM). We address the problem
of solitonic string quantization in this case. As well-known, only crfitical
strings with superconformal WSSMs are self-consistent in ultra-violet (UV)
domain. Thus, we look for the appropriate UV completion of the low-energy
non-conformal WSSM. We ague that for the solitonic strings supported in
well-defined bulk theories the UV complete WSSM has a UV fixed point which can
be used for string quantization. As an example, we consider BPS non-Abelian
vortices supported by four-dimensional (4D) \ntwo SQCD with the gauge group
U$(N)$ and $N_f$ quark multiplets where $N_f\ge N$. In addition to
translational moduli the non-Abelian vortex under consideration carries
orientational and size moduli. Their low-energy dynamics are described by a
two-dimensional \ntwot supersymmetric weighted model, namely, $\mathbb{WCP}(N,
N_f-N)$. Given our UV completion of this WSSM we find its UV fixed point. The
latter defines a superconformal WSSM. We observe two cases in which this
conformal WSSM, combined with the free theory for four translational moduli,
has ten-dimensional target space required for superstrings to be critical.
