query syntax (INNER JOIN)

I have a table that saves comma separated values, such as :  1,3,5
This values are the ID of records on a different table, called "Admintags"

When I add a record for a 'casecomment' one of the columns is called 'tags'  and this is where I save those comma separated values.

I have the following query:

 SELECT  
			a.CaseID ,
            a.tags,
            a.Comments
          
    FROM    dbo.Casecomments a

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That will return the following values:
caseid  | tags  | comment
30638  |  1, 5  | Client will be traveling to Mexico City from Dec 15th until Jan 2nd.

What I need the query to return is the value of those tags from the 'tags' table. The tags table is very simple, it only has two columns
id = the ids saved above
tag_text = the text value of the tag, this is what I need in return:

30638 |  Travel date, Billing | Client will be traveling to Mexico City from Dec 15th until Jan 2nd.

which are the corresponding values of 1 and 5 in the "Admintags" table.

1	Travel Date
2	Agreement
3	Billing
4	Contact method
5	Email 

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How can I do an inner join to display those values instead of the ID's that I have in the casecomments table ?