Applying for ILR

Hi All,

I hope someone can guide me through the right path with my immigration query.

So I'm a Non-EU citizen who was married to an EU-National a few years ago. I was granted a UK Residence card (Type of permit: Family member - EU residence) valid for 5 years starting from May 2016 - May 2021.
Unfortunately, we started having relationship issues and our divorce was finalized on October 2019. After I received the decree of absolute, my solicitor applied for EU settlement scheme using the divorce documents and I was granted Pre-Settlement status. I still have my EU Residence card BRP and I have been using it as its still valid (May 2016 - May 2021).

Now my question is, when is the earliest I can apply for ILR and what form do I need to be looking at?
Also, what are the costs involved if I have to do this by myself rather than going to a solicitor.

Your advice and help will be much appreicated.

Thanks

Bump