How to compress an hexadecimal number into a short string?

Projects Programming
18

If I try

byte tagEPCBytes[50][12];

for (byte x = 0 ; x < tagEPCBytes ; x++)
      { 
        tagEPCBytes[counter][x] = nano.msg[31 + x];
        Serial.print(nano.msg[31 + x]);
        Serial.print(F(" "));
      }

I get the following errors

error: invalid types 'byte {aka unsigned char}[int]' for array subscript

         tagEPCBytes[counter][x] = nano.msg[31 + x];


                            ^


invalid types 'byte {aka unsigned char}[int]' for array subscript

I tried to change the type of tagEPCBytes[50][12]; to int or char. No one works.