Connecting cooker to UK 3 pin socket
The electric cooker should have an installation manual. Most electric cookers in the UK are not plugged into a normal 13A wall outlet/socket. They are hardwired to a dual-pole cooker switch on a dedicated cooker circuit (e.g. a dedicated 32A circuit).

A typical cooker instructions will say something similar to this example.


  The cooker must be connected by a competent
  person  such  as  one  who  is  a,  NICEIC  registered
  contractor to a suitable double-pole control unit with
  a  minimum  rating  of  32A  and  a  minimum  contact
  clearance  of  3mm  (applicable  to  newer  properties,
  older properties where a 30A double pole control unit
  and a minimum contact clearance of 3mm is
  acceptable).
  The double pole control unit should be fitted
  adjacent to the cooker, in accordance with IEE
  regulations.  The  control  unit  must  be  within  2  metres
  of  but  not  directly  above  the  appliance  and  should
  be  easily  accessible  in  the  event  of  an  emergency.
  The  power  supply  cable  should  conform  to  B.S.6004
  with  a  conductor  size  of  6mm2,  minimum.
  Access  to  the  mains  terminals  is  gained  by
  removing  the  rear  access  cover.  The  mains  cable
  must  pass  through  the  cable  clamp  adjacent  to  the
  terminal  block.  Sufficient  cable  should  be  used  to
  allow  the  cooker  to  be  pulled  out  for  servicing.
  Ensure that the mains cable is routed away
  from any brackets affixed to the rear panel and
  is not trapped to the rear wall when pushing the
  cooker  into  position  between  cabinets


Examples of the required diversity calculations can be found online. For example: https://www.tlc-direct.co.uk/Book/6.5.2.htm

In your photo of your cooker's connectors, the multiple live and neutral connections appear to be each be connected by a copper bus bar. This presumably means that you can attach the supply to any of the screw terminals (brown to an "L", blue to an "N"). Don't use 13A flex or a 13A plug, it'll eventually blow the fuse or catch fire.