From Setup, enter Communities in the Quick Find box, then select All Communities -- > Then Click on builder
To access Community Builder:
From the global header menu in Community Workspaces or Community Management, click Community Workspaces | Builder or Community Management | Go to Community Builder.
From the All Communities page in Setup, click Builder next to the community name.
From a community, click Community Builder in the profile menu.
Did you enable Communities in your org ? If not, Setup-->Communities-->Communities Settings-->Enable Communities Once you enable, You can see the 'All Communities' option. From that, You can create a Community and open 'Community Builder' and all.
From Setup, enter Communities in the Quick Find box, then select All Communities -- > Then Click on builder
To access Community Builder:
https://help.salesforce.com/articleView?id=community_designer_ui.htm&type=5
Did you enable Communities in your org ? If not, Setup-->Communities-->Communities Settings-->Enable Communities
Once you enable, You can see the 'All Communities' option.
From that, You can create a Community and open 'Community Builder' and all.
Please let us know, if this helps.
Thanks,
Govindaraj.S
If you are using standard one then you will not get Builder.
If you are using Lightning then you will get Builder Option.
Please let me know if you have any queries.
Thanks,
Murali