Bus to leroy merlin

I think you will have to look hard and will struggle 

Yes  you are new to Spain     there is very little in the way of public transport       maybe a taxi but ask the cost    it is not that far 

but  in  Los Alcazares    try and find    juangalo    a biggish  Bricoage    (from Alidi    go towards the mar minor   at the first roundabout

go right      they even speak English      and much cheaper than  Leyroy Merlin

there is a very large  Leyroy Merlin in Cartagena     you may find a "bus"  from  Los Alcazares    

or buy on line       hope this helps