There are two scenarios.
- WhatsApp Chat is on the Android Device
- WhatsApp Chat is backed up on Cloud Drives
WhatsApp Chat is on the Android Device
If all your WhatsApp chats are on the Android Device and have not taken a chat backup then... Please use --> Move from Android to iPhone, iPad, or iPod touch - Apple ... Select WhatsApp App while selecting which data you want to get moved from an Android to iOS.
WhatsApp Chat is backed up on Cloud Drives
WhatsApp Chat backed on any Cloud Drive may not get fetched. The Move process cannot extract data from Google Drive or any other Drive where the chat backups are stored using an Android device, I presume iCloud Drive is not one of them. My experience says you can't transfer the WhatsApp Backup which was done using an Android because on Android, WhatsApp, chat history is not stored on iCloud, on iOS it is.
That may be possible with third-party software. Warning!; WhatsApp data through third-party software has the risk of data being compromised. Because the data will be churned through third-party servers, which may or may not be encrypted. Be judicious while selecting the software and taking this call.
If you had enabled WhatsApp Chat backup then I am sorry you may need to contact the app developer here --> App Support or WhatsApp FAQ Or Restoring your chat history - WhatsApp FAQ or Contact WhatsApp
