Although the Pegasus Conditions of Carriage specify
9.3.1. For all Pegasus flights our passengers will have a limited Checked Baggage allowance in terms of the number of pieces, weight and dimensions of their baggage, identified in accordance with the Package based on which their Ticket is issued.
in fact, nowhere is any limit on pieces specified. Indeed, if there were such a limit, Pegasus would surely impose a surcharge for exceeding the limit, but all such excess baggage fees are based solely on weight.
Broadly speaking, a flight with checked baggage limits set according to the weight concept does not impose a maximum number of individual bags. Theoretically, you could check 10 bags each weighing 2 Kg if you preferred. The airline may enforce a maximum weight or dimensions for any individual bag, of course.
(Weight concept remains the norm in most of the world; piece concept, where a fixed limit is set per bag and then a limit set on the number of bags, was used primarily to/from or within North America, although several major non-North American airlines have adopted it for all their routes in recent years.)