I have 240ml silicone bilateral for 12 yrs. I would like to know what size of silicone implants would be better for me. (photo)

Based on your photos, I would agree with your surgeon in the selection of a 400cc. However, I would not choose "super high" and would probably work the capsule but not change them to the subglandular plane. Good luck

Thank you for the question and pictures. In regards to specific size/profile of breast implant, despite good intentions, online consultants will not be able to provide you  with  meaningful specific advice.  Ultimately, in person consultation with well experienced board-certified plastic surgeons will be necessary. Careful measurements, dimensional planning, and careful communication will be key.
Generally speaking, the best online advice I can give to ladies who are considering revisionary breast augmentation surgery ( regarding breast implant size/profile selection) is:
1. Concentrate on choosing your plastic surgeon carefully.  Concentrate on appropriate training, certification, and the ability of the plastic surgeon to achieve the results you are looking for. Ask to see lots of examples of his/her work.  2.  Again, have a full discussion and communication regarding your desired goals with your plastic surgeon. This communication will be critical in determining which operation and/or breast implant size/type/profile will most likely help achieve your goals.
In my practice, the use of photographs of “goal” pictures (and breasts that are too big or too small) is very helpful. I have found that the use of words such as “natural” or "C or D cup" etc means different things to different people and therefore prove unhelpful.
 Also, as you know, cup size varies depending on who makes the bra; therefore, discussing desired cup  size may also be inaccurate.   
3.  Once you feel you have communicated your goals clearly,  allow your plastic surgeon to use his/her years of experience/judgment to choose the breast implant size/profile that will best meet your goals.  Again, in my practice, this decision is usually made during surgery.  The use of temporary intraoperative sizers, viewing the patient's breasts in the upright and supine position, are very helpful during the breast implant selection process.
I hope this, and the attached link ( dedicated to revisionary breast surgery concerns), helps.

Breast implant selection is best done in the setting of a formal consultation with a board certified plastic surgeon.

Choose your surgeon carefully; this is the most important decision you will make in regards to your breast augmentation. All members of the American Society for Aesthetic Plastic Surgery are board certified in plastic surgery with experience in cosmetic surgery. surgery.org will give you a list of such surgeons in your area.

Come to your consultation prepared to discuss your aesthetic goals - bust fullness, figure balance and breast shape. Bringing photos to illustrate your point can be helpful. After an examination your surgeon will be able to discuss and recommend particular implants that will best achieve your aesthetic goals. Some surgeons will use various tools to help patients choose their implants. Implant sizing, 2D photography, 3D photography and photo gallery review are a few. Ultimately I believe the patient should make the final decision with regards to the implant. I believe the surgeon's role is to offer advice; I do not think the surgeon's role is to dictate which implants patients choose.