If the keyboard does not have a standard (DIN type) midi connector, but does have a USB port, then you'll need a USB connector.
Then, it depends on what you need to connect to.
If you need to connect to something that also has USB, then a USB/USB cable should be OK. If you need to connect to something that does have DIN type midi connectors, then there are various USB/MIDI connectors/converters, but note, some of these are better than others. In particular, the cheaper ones can be slow, giving rise to 'latency' issues. Read the reviews before you buy, and remember that you get what you pay for.
Geoff