The application form asks:
For either the UK or any other country, have you ever been:
- Refused a visa
- Refused entry at the border
- Refused permission to stay or remain
- Refused asylum
- Required to leave
- Excluded or banned from entry
It then asks for further details (what happened, what country, when, and free text details). It will ask for it for as many events as necessary.
So, as you will not lie about it, they will know.
If you think about lying about it, don't. There are good chances they will find out, and if they do, you'll be in a lot of trouble, and will not only be refused a visa, but will most probably be banned for many many years.
Having been refused so many times is definitely not in your favour, though we don't know the details about those rejections, when they happened, why they happened, and if your circumstances may have changed since then. Even if the reason for your visa request has changed, you should most definitely make sure you address all the issues they raised before applying for a UK visa.