The phrase “in Arabic language” in Arabic is more naturally: في اللغة العربية So there are two common expressions: باللغة العربية = “in Arabic” (used for language labels like “write in Arabic”) في اللغة العربية = “in the Arabic language” (literal wording of your phrase) If you’re just labeling a language (like on menus, apps, or forms), باللغة العربية is the most common.
“In Arabic language” in Arabic is: باللغة العربية If you also want the phrase written more naturally in context (for example, “in the Arabic language”), it’s the same: باللغة العربية
الجملة بالعربية الفصحى هي بالفعل: "ما الذي تود مني أن أترجمه إلى اللغة العربية؟" وترجمتها إلى الإنجليزية: “What would you like me to translate into Arabic?”