Hi @futureyoon
Thank you for getting in touch with us!
Sorry to say, this is a very specific customization for a plugin, you can find this level of configuration ability inside the theme. However, sharing a snippet that will help you to override the existing CSS you would like. Update the color code and px amount.
Appearance > Customize > Additional CSS
.directorist-listing-single {border: 1px solid #dddddd; }
.directorist-listing-single .directorist-listing-single__meta{border-top: 1px solid #EFF1F6;}
Feel free to let me know for more help.
Regards,
Sheikh Faysal