You can definitely add more than one LDAP server and additional Automated Device Enrollment and Volume Purchasing tokens from other Apple Business Manager accounts. Be sure to reassign computers and mobile devices to your Jamf Pro server when ready.
With regard to LDAP connections, I think your biggest problem to solve may be usernames. LDAP servers are searched in the order they were added. I believe if matches are found in the first LDAP server, Jamf Pro stops and returns the results. It won't search in subsequent LDAP servers. Therefore, you need to determine whether both Active Directories follow the same naming convention (first initial + last name, first.last, etc.). If they don't, there's nothing to worry about.
Also note that the more LDAP servers you have, the longer it takes for Jamf Pro to return results. This may be milliseconds, which is acceptable. If lookups take far longer, you can do a few things to optimize how you search in Jamf Pro. Jamf Support could help you with that.
i spoke to our vendor about the ABM, fortunately, we were able to have the records released from the company we acquired and then sent to our ABM.
Thank you for the responses!