How can I change my meta_query to SQL wpdb query?

Several things, Firstly you can add the following for pagination:

'paged' => ( get_query_var('paged') ? get_query_var('paged') : 1 )

This removes the need for the array_merge. Otherwise your existing code is fine except for some indentation. I would add the rest of the query though, e.g. defining the post type, the posts per page, etc

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