guide about copy paste KK/KK party mod to KKS and how to totally convert mod card here https://f95zone.to/threads/info-guide-about-koikatsu-kk-party-mod-to-koikatsu-sunshine-compability-and-how-to-convert-all-koikatsu-mod-card.93152/ or here https://www.reddit.com/r/KoikatsuSunshine/comments/pg9jdu/info_guide_about_koikatsu_kk_party_mod_to/

so try converted your mod card / vanilla card and put the clothing / costumes you wanted.