open iOS iPad simulator with React Native

Get device list with this command

xcrun simctl list devices

Console

== Devices ==
-- iOS 13.5 --
    iPhone 6s (9981E5A5-48A8-4B48-B203-1C6E73243E83) (Shutdown) 
    iPhone 8 (FC540A6C-F374-4113-9E71-1291790C8C4C) (Shutting Down) 
    iPhone 8 Plus (CAC37462-D873-4EBB-9D71-7C6D0C915C12) (Shutdown) 
    iPhone 11 (347EFE28-9B41-4C1A-A4C3-D99B49300D8B) (Shutting Down) 
    iPhone 11 Pro (5AE964DC-201C-48C9-BFB5-4506E3A0018F) (Shutdown) 
    iPhone 11 Pro Max (48EE985A-39A6-426C-88A4-AA1E4AFA0133) (Shutdown) 
    iPhone SE (2nd generation) (48B78183-AFD7-4832-A80E-AF70844222BA) (Shutdown) 
    iPad Pro (9.7-inch) (2DEF27C4-6A18-4477-AC7F-FB31CCCB3960) (Shutdown) 
    iPad (7th generation) (36A4AF6B-1232-4BCB-B74F-226E025225E4) (Shutdown) 
    iPad Pro (11-inch) (2nd generation) (79391BD7-0E55-44C8-B1F9-AF92A1D57274) (Shutdown) 
    iPad Pro (12.9-inch) (4th generation) (ED90A31F-6B20-4A6B-9EE9-CF22C01E8793) (Shutdown) 
    iPad Air (3rd generation) (41AD1CF7-CB0D-4F18-AB1E-6F8B6261AD33) (Shutdown) 
-- tvOS 13.4 --
    Apple TV 4K (51925935-97F4-4242-902F-041F34A66B82) (Shutdown) 
-- watchOS 6.2 --
    Apple Watch Series 5 - 40mm (7C50F2E9-A52B-4E0D-8B81-A811FE995502) (Shutdown) 
    Apple Watch Series 5 - 44mm (F7D8C256-DC9F-4FDC-8E65-63275C222B87) (Shutdown) 

Select Simulator string without ID here is example.

iPad Pro (12.9-inch) (4th generation)

Final command

iPhone

• iPhone 6s

react-native run-ios --simulator="iPhone 6s"

• iPhone 8

react-native run-ios --simulator="iPhone 8"

• iPhone 8 Plus

react-native run-ios --simulator="iPhone 8 Plus"

• iPhone SE (2nd generation)

react-native run-ios --simulator="iPhone SE (2nd generation)"

iPad

• iPad Pro (12.9-inch) 4th generation

react-native run-ios --simulator="iPad Pro (12.9-inch) (4th generation)"

• iPad Air (3rd generation)

react-native run-ios --simulator="iPad Air (3rd generation)"

• iPad (7th generation)

react-native run-ios --simulator="iPad (7th generation)"

--simulator flag is what you are looking for

For example react-native run-ios --simulator 'iPad 2' will run the app on iPad 2 simulator.

As a side node, if you need to get list of available simulators with their names use xcrun simctl list devices