what do I need to connect 2 extra monitors to my iMac

Video Support and Camera

• 1080p FaceTime HD camera
• Simultaneously supports full native resolution on the built-in display at 1 billion colors and:  
• • One 6016-by-3384 (6K) external display at 60Hz with support for 1 billion colors, or
• Two 6016-by-3384 (6K) external displays at 60Hz with support for 1
• billion colors (requires AMD Radeon Pro 5700 or AMD Radeon Pro 5700
  • XT), or
  • One 5120‑by‑2880 (5K) external display at 60Hz with support for 1 billion colors, or
  • Two 3840-by-2160 (4K UHD) external displays at 60Hz with support for 1 billion colors, or
  • Two 4096‑by‑2304 (4K) external displays at 60Hz with support for millions of colors
• 
  
• Thunderbolt 3 digital video output
• Native DisplayPort output over USB‑C
• Thunderbolt 2, HDMI, DVI, and VGA output supported using adapters (sold separately)