If you are transferring your content from an Android to an iPhone, you can download this app and follow the prompts: “Move iOS” https://support.apple.com/en-us/HT201196
If you are transferring from an iPhone to an Android or Android to Android:
Download the My Contacts backup app and launch on your iPhone. When the app (“MCBackup”) asks to access your contacts, tap OK. Tap Backup. Tap email, attach the VCF file to an email and send it to your Gmail account. Open up the email from your Android device, download the VCF file and import your contacts to the phone. As demonstrated by the image below, the VCF file allows you to either select specific contacts to import to your list or add the entire address book with the Add All X Contacts tab.