It does not appear that Arkansas Secretary of State issue separate identification numbers.
The link below provides some general information and also a phone number that you can call to confirm:
http://www.sos.arkansas.gov/bcs/documents/corporations/doing-business-in-ar.pdf
I assume you have registered appropriately with the state.
Here is another link to some FAQ's:
http://www.sos.arkansas.gov/Pages/siteSearch.aspx?q=llc
What did you find out?
Please use the following link to look up your Arkansas Secretary of State number.
You can type in the name of the company and be able to see the entity number on this site.
Arkansas SOS # search