so in my case, I want to know if I create a new organization and ask the support team to put the MX67W in the new organization, should i also have a new dashboard license, and also if I can create this site-to-site VPN.
1. In one Organization all the firewall (MXes) should have of one license type. [Enterprise / Adv / SDWAN]
2. We need to have separate set of license for every Organization.
3. We can always have Site-to-Site VPN between two Organizations - but this will be a 3rd Party VPN configuration. AutoVPN will not be possible. I also understand we need public Static IPs at both the ends for this configuration.
It seems to me that the key thing here is to unclaim the license you claimed as a renewal, as per the instructions in the document you referenced.
When you claim a renewal in a co-term Organization, you must include a license for every device that you want to carry on working afterwards (i.e., including your MX67's)
Ajit is right that you must have the same license level for all MXs in an Organization.
If you want Advanced Security, then once you have unclaimed the renewal you should ask Support to convert the Organization to Advanced Security (you will see the license time, til renewal shortens - as Adv Sec uses MX license time at twice the rate of Enterprise)
You will then be able to claim the license with the MX250 Adv Sec into your Adv Sec Organization.
With all your MXs in the same Organization, setting up (Auto)VPN between them will be so much easier and more powerful than setting up non-Meraki VPNs between the MXs in different Organizations.