There are a number of Free SEO Tools on the internet to help you with search engine optimisation on your website.

Here are a couple of helpful website pages that should give you all the tools you require:

SEO Book

Ahrefs Free SEO Tools

Free SEO Tools 1

You might also like to have a look at SEO Powersuite which is a complete suite of SEO tools that are very helpful and comprehensive.

You can download and use the suite free of charge to see how it performs.