I am looking to buy and install a mikrotik wireless router and a repeater to install the router in the garden then the repeater inside the house (without linking the repeater to a network cable just a power source).
what are the best mikrotik equipment that can do such job high power wireless.
There are several examples of these types of bridges in the FAQ and Examples documentation. If I understand you correctly you want a router connected to an Internet supply in your garden to then connect wirelessly to your house where it will connect to an internal Ethernet in the house.
If this is the case then 2 411 boards with wireless cards and simple antennas should suffice for this purpose. The antenna choice will depend on distance, obstructions and general environment. Remember more powerful is not always better, just like if you try to hand over a baton in a relay too fast.