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

You can't convert a jpeg to a raw file. The raw format is a proprietary format for files coming out of the camera. If you could convert, there would be no benefit. Raw files are typically 12 or 14 bits per color channel, while jpegs are 8. You can't recover the missing 4 or 6 bits. The TIFF file format does not compress the data. That's why they're so big. Files can be saved as jpegs. You will lose data in going from raw to jpeg (those extra 4 or 6 bits). However, if you save at the highest quality jpeg, you won't lose any data from that point on. However, if you use any but the highest quality, you will lose data and it will get worse from generation to generation.