Should i convert my old jpeg files to RAW or is TIFF files better?

If you want true RAW photos you'll have to shoot them that way. I'd say it all depends on what they're being used for. If going to be published in a magazine or some such then RAW or TIFF is a good choice. If you're viewing them at home on your computer there's no real difference on your monitor between RAW and jpg because the monitor is only capable of so many mp anyway.