it looks as if your trying to convert a byte to a string

I Dont know how to store a string as a variable, but you need to set the string variable to that byte
something like

UNIT VAR BYTE
mystring VAR ???
unit = v0(x)
mystring = unit
LCDOUT $FE,1,DEC UNIT," ", mystring," ",BIN UNIT," ",HEX UNIT