Your desired URL is probably already in use. A website name generator will check this and suggest alternatives. You can often simply use a different top-level domain. Instead of .com, you could end your address with .org, for example. However, be sure to pay attention to trademark law – it could be that a name may already be protected and you are not allowed to use it in the URL.
However, the domain generator also suggests other term combinations that are still available and could be a good choice for your website. If you absolutely have to have a domain that is already taken, you can try to contact the owner. They may not be using the address at the moment and may be willing to sell the domain to you. However, this could end up being expensive depending on the price they come up with.
Since the domain name generator suggests numerous options, you can also think about registering several domains at once. You then either use the other URLs as redirects or secure them for brand protection and to prevent direct competition.