How do you write a letter of come back for a job i left 1yr ago for some personal reasons i want to go back to that same company can someone give a sample letter?

All business letters should have the same structure:

Date

Name of person addressed
Name of Company or Organization
Address of Company or Organization
City, State, Zip (or equivalent depending on country)

Dear Name,

first paragraph: a sentence or two stating why you are writing.

second paragraph: give the facts and information supporting your request. This can actually be more than one paragraph or if several facts needed, use bullets. Don't use emotional language or go off the target of your request.

third paragraph: tell the addressee what you want them to do or what you want to happen. Be clear without emotional language or going off the target. Give your address and/or phone number at the end to be sure it's easy for the addressee to find.

Use Sincerely or Thank You,

Signature
Print or Type Your Name

This is a universal format. Good for any type of business letter. It is designed for a positive response even if the answer is no, leaving a good impression for further negotiations should that be necessary.