Re-interpreting your question: To make your old Sony TV usable, you need to purchase an external digital tuner. Here's an example: https://www.bestbuy.com/site/mediasonic-digital-converter-box-with-dvr-black/6293207.p?skuId=6293207. You'll also need a HD antenna. If you're in an urban setting, something like this: https://www.bestbuy.com/site/mohu-leaf-30-indoor-hdtv-antenna-black-white/3488024.p?skuId=3488024.
You also might want to consider getting a new flat screen TV and an HD antenna. It will give you a vastly improved picture over the old Sony TV. Good 36 to 43 inch TV's can be purchased for under $200 now. With some shopping over Thanksgiving, you may be able to find one in the $100 to $150 range.