TOEIC and TOEFL aren't recognised now by the UKVI so you wont be able to use that test in your application. If you are planning to take IELTS, the minimum requirement for the settlement/spouse/fiancee visa is just the General Training test. You need to get at least 4.0 grade in speaking and listening. If you are planning to work as a nurse (or other professional work that requires a higher mark for English) here in the UK, Academic Test is the one you need to take, with passing mark of at least 7.0 for all the categories (speaking, listening, reading, writing).