Hello mark_apple,
When you transfer your data from Android, your contacts are put in the default account on your iPhone. To change the default account, follow these steps:
If you set up multiple accounts in the Contacts app, you can choose a default account to add new contacts to. Just go to Settings > Contacts > Default Account and choose an account.
This information and more can be found here: Manage and delete contacts on your iPhone, iPad, or iPod touch
If your default account on your iPhone is iCloud, then these contacts will be transferred to iCloud. If you run into any issues with the data transfer, please provide more details.
Take care!