TM6 is not a domain, it is a helix. In the second link you posted, all trans-membrane helices are shaded in light blue, and labeled TM[1-7]. Then you have extracellular loops (ECL[1-3]) and intracellular loops (ICL[1-3]). The residues you want most likely are PHTQ in ICL3 that precedes TM6.
Thank you so much for your help. I wanted to ask you one more question, if you can please help me with that. How to determine what all residues are present in the extracellular site of ECL-2 loop region.