Hi, here is a conversion table for needles and yarns. It doesn't have the # system I don't think, like #4 is worsted, but one worsted can be quite different from another, so you really need to watch recommended gauge.
LINK
You can twist a stitch by knitting into the back of it. There are also other things that may be called twists like knitting 2 stitches together, but not letting them off the needle and then going back and knitting the first stitch again then letting them off the needle.