Usually, this page is included just after Table of Contents. As far as the length is concerned, there is no restriction.
The basic purpose to include acknowledgement page is just to pay a thankful note for all those people who have supported you in carrying out your research.
For academic contributors whom you choose to mention in your acknowledgements, you should use their full names and titles.
However, if you are mentioning friends, you might consider only using first names to protect their identities.
Take a look back at your list of contributors, and be sure to mention the members of academia who helped you complete your dissertation or thesis.
Again, you only have room for major contributors, not your freshman biology professor.
Though you can include several names in your acknowledgements, you should only include names of people who actually did help you during your dissertation or thesis journey because of limited space and reader patience.
In general, you should keep your acknowledgements on one full, double-spaced page of the same font type and size that you are using throughout the rest of your paper.
When you mention these people in your acknowledgements, remember to state specifically how they helped you.
This will mean a lot to these people, and they will be grateful that you remembered exactly what they did for you along the way.