Marek,
is this close to what you are trying to do:
In[1]:= pom2 = {"{0, 90012}", "{0, 90013}", "{0, 90016}",
"{0, 90022}", "{0, 90034}", "{0, 90042}", "{0, 90102}",
"{0, 90106}", "{0, 90115}", "{0, 90131}", "{0, 90132}",
"{0, 90137}", "{0, 90153}", "{0, 90214}", "{0, 90222}",
"{0, 90226}", "{0, 90230}", "{0, 90234}", "{0, 90239}",
"{0, 90247}", "{0, 90304}", "{0, 90306}", "{0, 90312}",
"{0, 90316}", "{0, 90323}", "{0, 90325}", "{0, 90328}",
"{0, 90331}", "{0, 90332}", "{0, 90333}", "{0, 90336}",
"{0, 90344}", "{0, 90349}", "{0, 90351}", "{0, 90354}",
"{0, 90358}", "{0, 90408}", "{0, 90413}", "{0, 90416}",
"{0, 90417}", "{0, 90419}", "{0, 90438}", "{0, 90447}",
"{0, 90448}", "{0, 90453}", "{0, 90457}", "{0, 90523}",
"{0, 90549}", "{0, 90616}", "{0, 90618}", "{0, 90638}",
"{0, 90640}", "{0, 90642}", "{0, 90649}", "{0, 90652}",
"{0, 90708}", "{0, 90713}", "{0, 90715}", "{0, 50733}"};
In[2]:= If[(IntegerDigits@ToExpression[#][[2]])[[1]] == 9,
StringReplace[#, {" " -> "", "," -> ""}],
StringExpression["{",
Sequence @@ (ToString /@ (IntegerDigits@ToExpression[#][[2]])),
"}"]] & /@ pom2
Out[2]= {"{090012}", "{090013}", "{090016}", "{090022}", "{090034}", \
"{090042}", "{090102}", "{090106}", "{090115}", "{090131}", \
"{090132}", "{090137}", "{090153}", "{090214}", "{090222}", \
"{090226}", "{090230}", "{090234}", "{090239}", "{090247}", \
"{090304}", "{090306}", "{090312}", "{090316}", "{090323}", \
"{090325}", "{090328}", "{090331}", "{090332}", "{090333}", \
"{090336}", "{090344}", "{090349}", "{090351}", "{090354}", \
"{090358}", "{090408}", "{090413}", "{090416}", "{090417}", \
"{090419}", "{090438}", "{090447}", "{090448}", "{090453}", \
"{090457}", "{090523}", "{090549}", "{090616}", "{090618}", \
"{090638}", "{090640}", "{090642}", "{090649}", "{090652}", \
"{090708}", "{090713}", "{090715}", "{50733}"}
