On your iPhone or iPad, go to Settings
Tap your name
Tap iCloud
Turn on Contacts if it is not already enabled
On a computer, open iCloud.com
Sign in with your Apple ID
Open Contacts
Select all contacts
Click the gear icon
Choose Export vCard
Save the .vcf file to your computer
Open Google Contacts
Sign in with your Gmail account
Click Import
Select the .vcf file
Click Import
Wait for the contacts to finish uploading
Check Gmail contacts to confirm the import
Delete the exported .vcf file if you no longer need it