Please look at the following below links which may help you in your analysis:

https://www.vernier.com/experiment/chem-o-5_separation-of-organic-compounds-by-acid-base-extraction-techniques/

https://authors.library.caltech.edu/25034/19/BPOCchapter18.pdf

Thanks

Acidify your solution to pH below the pKa of the acid.

Thanks Isam Eldin Hussein Elgailani and Yurii V Geletii

Hi Ahmed J. Al-Musawi, generally you can prepare a concentrated aqueous solution of your sodium carboxylate and add hydrochloric acid until the mixture is acidic. The following work-up depends on the nature of your carboxylic acid. If it is a solid, chances are that it will precipitate upon acidification. Then it can be isolated by filtration. If the carboxylic acid doesn't precipitate, it can be extracted from the aqueous solution with diethyl ether. The diethyl ether phase can then be dried (e.g. using anhydrous MgSO4) and the ether evaporated after filtration.

This really solves my problem right now. Thanks.

A stronger acid added to the solution is expected to convert the salt of the weaker acid present in the solution to the weaker acid and salt of the stronger acid.