Had left testicular removal in 2007 due to testicular cancer and now diagnosed hydrocele in right testicular. what is the safe effective treatment ?

See urologist: If the problem on the right side is a simple hydrocele, you can have a minor operation to get rid of it.

U-Sound then Surgery: Ultrasound to make sure it's a simple hydrocele. Then have urologist perform straightforward trans-scrotal hydrocelectomy.

See below: A scrotal ultrasound will confirm a diagnosis of hydrocele. While this can be corrected with a relatively simple outpatient operation, if it is not really hurting or bothering you in any way, i would advise against it. All surgery, no matter how "minor", can have complications, and in your case, this is the only testicle you have left, and is the only thing making testosterone and sperm!