SQL & PL/SQL :: Oracle String Replacement

I am facing one problem when replacement a string with some other string .For better understanding example is as follows:

I have a string :

String1 varchar2(200):= '2, ,129, ,3,Mia Abc,7,TPS,7,Mia X';

In my replacement table I have values like :-

Trn_value New_Value

Mia Abc Miahjdfrt
TPS Erf
Mia X' RYe

Now I want to replace the string as :
'2, ,129, ,3,Miahjdfrt,7,Erf,7,RYe'

I used replace(String1, Trn_value,New_Value); But it is not working.