Please help.

I got reference for my I-140 from Nbraska center, as follow:

It is noted that you subbitted a letter addressed to the CIS regarding the terms of the beneficiary's employment. Please submit a complete copy of the actual letter and /or contract offering employment to the beneficiary (addressed to the beneficiary) issued by the appropriate hiring authority pursuant to title 8, code of federal regulations 204.5(i)(3).

I don't have the letter regarding the current position (it changed, and my salary changed). Any one can kindly tell me what I shoud do? Thank you very much.