United Kingdom – Letter of authorization to collect the visa

I would like to authorize another person to collect the visa on my behalf.

I have taken a hard copy of the authorization letter from here.

He says that I have to give the reference number of the global VFS receipt that starts with KTM. I do not have a reference number that starts with KTM.

I am able to find reference numbers that start with GWF ***, VFSS *** and XYZ ***.

So, can someone tell me where to find this reference number that starts with KTM?